Gaskets are often used as a seal between mating mechanical components. One common application involves gasket placement between the engine block and the cylinder head of an internal combustion engine. Cylinder head gaskets typically extend around the cylinder bores to provide a combustion seal, maintaining the high temperature gases of combustion with the cylinder bores. At the same time, the gaskets also seal fluid flow openings such as coolant and oil openings to prevent undesirable mixing. In addition, such gaskets prevent leakage by sealing the areas around the bolts which connect the cylinder head and engine block. Gaskets bear the load from a bolted connection between the head and the block and they rely upon that load to provide a seal.
It is known to locate one or more additional metal layers, or pieces of layers, both of which may be referred to as shims, between the active gasket layers. A shim is typically made of metal and may have a constant thickness. Shims typically are not compressible and thus may assist in creating a sealing feature for the gasket when the gasket is compressed.
Shims, however, do have some significant disadvantages. More particularly, when the gasket is compressed the loading of the shim between the cylinder bores is typically poor. Typically, this is because the mechanical fasteners connecting the cylinder head and the block are distant from the land area between the bores. Generally, as the distance from a mechanical fastener increases, the compression force provided by that mechanical fastener decreases. If the shim is not properly loaded, it may result in premature failure or overall poor performance of the gasket.
It is also known to use coatings for various purposes in gaskets. Coatings may be advantageous as they can be inexpensive, depending on their composition and method of application, to apply to gasket material. Some coatings are provided with a predetermined thickness in order to limit compression in certain areas of a gasket.
It would be advantageous to utilize the inexpensive and ease of use charateristics of a coating with the compression adding features of a shim without incurring the disadvantages associated with the shim and coating.